Department of Chemistry, Seoul National University, Seoul 08826, Korea.
Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, UK.
Mol Plant. 2017 Feb 13;10(2):274-284. doi: 10.1016/j.molp.2016.11.009. Epub 2016 Nov 25.
Upon exposure to light, developing seedlings undergo photomorphogenesis, as illustrated by inhibition of hypocotyl elongation, cotyledon opening, and leaf greening. During hypocotyl photomorphogenesis, light signals are sensed by multiple photoreceptors, among which the red/far-red light-sensing phytochromes have been extensively studied. However, it is not fully understood how the phytochromes modulate hypocotyl growth. Here, we demonstrated that HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1), which is known to either act as E3 ubiquitin ligase or affect chromatin organization, inhibits the transcriptional activation activity of PHYTOCHROME INTERACTING FACTOR 4 (PIF4), a key transcription factor that promotes hypocotyl growth. Consistent with the negative regulatory role of HOS1 in hypocotyl growth, HOS1-defective mutants exhibited elongated hypocotyls in the light. Notably, phyB induces HOS1 activity in inhibiting PIF4 function. Taken together, these observations provide a molecular basis for the phyB-mediated suppression of hypocotyl growth in Arabidopsis.
在光的作用下，发育中的幼苗会进行光形态建成，表现在下胚轴伸长、子叶张开和叶片变绿受到抑制。在下胚轴光形态建成过程中，多种光受体感知光信号，其中红光/远红光光受体光敏色素已被广泛研究。然而，光敏色素如何调节下胚轴生长还不完全清楚。在这里，我们证明了高表达渗透响应基因 1（HOS1），它既可以作为 E3 泛素连接酶，也可以影响染色质组织，抑制促进下胚轴生长的关键转录因子 PHYTOCHROME INTERACTING FACTOR 4（PIF4）的转录激活活性。与 HOS1 在抑制下胚轴生长中的负调控作用一致，HOS1 缺陷突变体在光照下表现出伸长的下胚轴。值得注意的是，phyB 诱导 HOS1 的活性来抑制 PIF4 的功能。综上所述，这些观察结果为 phyB 介导的拟南芥下胚轴生长抑制提供了分子基础。
